Camera comprising a pick-up tube and a lens objective with a variable effective aperture ratio



WV 7 w au-mun nuum Jan. 13, 1959 J SEUR 2,868,100

CAMERA COMPRISING A PICK-UP TUBE AND A LENS OBJECTIVE WITH A VARIABLEEFFECTIVE APERTURE RATIO Filed Oct. 26, 1955 75 If A 30 19 f 18 L 9 7 5j 10 6 1, 5 a r 9 I Q4 IH I r -10 BFQ/ 5 A I N V E N To R 1 CRISTIAANJACOHJS SEUR BY gpwf AGENT United States Patent CAMERA COMPRISING APICK-UP TUBE AND A LENS OBJECTIVE WITH A VARIABLE EFFEC- TIVE APERTURERATIO Referring to Fig. 1, reference numeral 1 designates the pick-uptube, constructed as an image inconoscope. It is provided with aphoto-cathode at 2, reference numeral 3 designates the electron gun ofthe tube. The electrical 5 conductors for the image iconoscope are notshown in chrisfiaan Jacobi SE1", Eilldhoven, Netherlands, Fig. l. Theimage iconoscope co-operates with the lens signor, by mesne assignments,to North American 4. The photo-cathode 2 is spaced apart from this lensPhilips Company! New York a corpora approximately by the focal distance.The light beams 5 tion of Delaware and 6 designate the main directionsof the extreme beams Application October 26, 1955, Serial No. 542,993captured by the photo-eathode-Z via the lens 4. Reference numerals 7 and8 designate the outer boundaries of the Claims Priority applicationNetherlands angular aperture a of the lens 4, when the diaphragm 9November 1954 is completely opened.

2 Clai ((31, 95-64) As stated above, a diaphragm co-operates with thelens 4. If this diaphragm is closed over a certain distance and A Camerais known which comprises a P -"P tube and occupies the position 9', theangular aperture is, of course,

a lens objective having a variable, effective aperture ratio. d d fromth initi l al a m the value [7. One example thereof is a televisionrecording camera om- The 18118 4 co-operates furthermore with the filter1o. prising a pick-up tube constituted by a icon s pe- .Jfhis filtercomprises a stretched, elastic film which is per- During operation theaperture ratio of the lens 0 may be varied, for example, in order toobtain a sharpness in depth for a particular scenery than for another.It is known that by increasing the aperture ratio of the objective agreater quantity of light strikes the image screen of the camera. Thisis, in general, no objection for the conventional film cameras andphotographic cameras; the conventional lightsensitve materials thereofhave a sufiicient resistance. However, with a camera comprising apick-up tube, a greater aperture ratio of the objective gives rise tothe risk that the light-sensitive element of the pick-up tube cannotstand these larger quantities of light.

In order to permit the use of great, effective aperture ratios of theobjective with the last-mentioned type of cameras, the camera accordingto the invention has the feature that a filter having a variablepermeability to light is arranged in addition on the path of the lightin front of the pick-up tube. This filter is constituted by an elastic,taut light-pervious skin provided with means to adjust its tension. Inthis camera the adjusting means for the aperture ratio of the objectiveand for the permeability of the filter to light are coupled with oneanother in a manner such that upon a variation of the effective angularaperture of the lens the permeability of the filter is varied inopposite sense. Thus, for example, with a larger effective apertureratio of the lens the permeability of the filter to light can bereduced, in a structurally simple manner, so that the luminous fluxstriking the pick-up tube does not increase directly proportionally tothe increase in effective aperture ratio of the objective. The mechanismcoupling the adjusting means of the diaphragm and the filter will bedesigned in accordance with the greater or smaller light-sensitivity ofthe screen.

The invention will be described more fully with reference to thedrawing.

Fig. 1 shows diagrammatically one embodiment of the pick-up tube u'sedin the camera according to the invention, comprising the lens objective(termed hereinafter the lens) the device to vary the aperture ratio(termed hereinafter the diaphragm) and the filter of variable lightpermeability (termed hereinafter the filter) and the mechanismcontrolling the diaphragm and the filter.

Fig. 2 is a front view of the filter with the associated stretchingdevice.

Fig. 3 shows partly in a view and partly in a longitudinal section thefilter, the diaphragm, the lens, the device controlling the filter andthe diaphragm and the guiding device for the filter.

Fig. 4 shows the control-device for the filter and the diaphragm in afront view, taken in the direction of the arrows IV-IV of Fig. 3.

greater Jective 20 vious to light and which may be constituted, forexample,

by an elastic synthetic substance. If this film is drawn radially to theoutside and is thus stretched, its thickness is reduced and itsfiltering or absorbing effect on the passing light will be smaller. Ifthe diaphragm 9 and the filter 10 are intercoupled in a manner such thatupon a variation of the effective aperture ratio of the lens the lightpermeability of the filter is varied in an opposite sense, it isachieved that even with a high aperture ratio of the lens 4 the quantityof light striking the photocathode 2 of the pick-up tube 1 will not besuch that it could not be worked up satisfactorily by this photocathode.

The said coupling is shown diagrammatically in Fig. 1. It is assumedthat by a radial displacement of the diaphragm elements, the apertureratio thereof can be varied. The diaphragm is provided with a couplingpiece 11, which is connected via a pivot 12, a connecting element 13 anda pivot 14 with the arm 15:: of a two-armed lever, which is rotatable at16 about a fixed point. In a similar manner the filter 10 is connectedvia a coupling piece 17, a pivot 18, a connecting element 19 and a pivot20 with the other arm 15b of the said two-armed lever. Upon a rotationof the two-armed lever about the point 16, the aperture ratio of thelens 4 and the light permeability of the filter 10 will be varied inopposite sense. The absolute ratio between the motion of the filter andthe diaphragm may be varied by suitable choice of the longer of thelever arms 15a and 15b.

With reference to Figs. 2, 3 and 4 one embodiment of the couplingmechanism between the filter and the diaphragm will be described.

The film 10, made from an elastic light-pervious synthetic substance, isprovided with a thickened edge 10a, which is held in clamping pieces 21.These clamping pieces have side surfaces 21a and 21b such that they canperform unhindered a certain radial movement (in the directions of thearows A and B). These clamping pieces are provided each on each sidewith opposite pins 22 and 23. The pins 22 are movable in radial slots24, provided in a stationary annular structural part 25. The pins 23 aremovable in arcuate guiding slots 26, provided in an annular structuralpart 27, rotatable about the system axis 0-0. The annular structuralpart includes the objective 28, held in a holder 29. Over part of itsinner periphery the annular structural part 27 is provided moreover witha tooth rack 30, co-operating with an outer tooth rack 31, provided onthe outer periphery of the diaphragm 32, held in a support 33. Thiscarrier cannot rotate with respect to the system axis CC.

This device operates as follows: It is assumed that the diaphragmconstructed as in iris diaphragm is substan- 26); upon a rotation of theannular element 27 in the 5 direction of the arrow D, the pins 23 willbe moved to the inner side owing to the shape of the arcuate slots 26,so that the clamping pieces 21 move in the direction B. Upon thismovement the clamping pieces are guided by the pins 22 moving in theradial slots 247 During this 10 movement the tension of the film 10decreases, so that the latter assumes a larger thickness and thus exertsa stronger light-absorbing effect. Upon a rotation of the element 27 inthe direction of the arrow D, the inner tooth rack 30 moves along theouter tooth rack 31 on the 15 outer side of the holder 33 of thediaphragm, so that the diaphragm is opened. Upon a further movement ofthe annular element 27 in the direction of the arrow E, the operationsare performed in an opposite sense.

What is claimed is: 20

l. Ad ia hragrn and filter arrangement for a camera including a lensobjective comprising a light-pervious filter constituted of an elastictaut film positioned?! the path of light, first means to adjust thetension of said film, second means to adjust the a rture ratio of said nlens ob ective, and maiis coupling said first and second" means wherebyupon variation of the aperture ratio of said lens the tension of saidfilm is varied to thereby change the light permeability of the filter inan opposite sense.

2. A diaphragm and filter arrangement for a camera including a lensobjective as claimed in claim 1 further comprising a rotatable annularelement mounting the light objective and provided with a plurality ofarcuate slots therein, a part of said coupling means projecting throughat least one of said slots whereby upon rotation of said annular membersaid aperture ratio of said lens objective is varied and the tension ofsaid film simultaneously varied in an opposite sense.

References Cited in the file of this patent UNITED STATES PATENTS2,431,824 Pach Dec. 2, 1947 FOREIGN PATENTS 444,074 Great Britain Mar.12, 1936

